1. Field of the Invention
The present invention relates to tubing sealers, and more particularly, to the configuration of the movable ground jaw cooperating with a fixed jaw to form a tear seal across liquid filled plastic tubing.
2. Description of the Prior Art
There is a continuing existing need for blood donors in order to meet the day-to-day hospital demand for blood. The collection of blood from donors is a critical function performed in all towns, cities and metropolitan areas as the need for fresh blood and plasma by hospitals never diminishes. During periods of national emergency, the need may be significantly greater. Consequently, various private and government related blood collection centers have been established at permanent locations and mobile blood collection units are employed to service remote areas or to obtain blood from donors at specific high density locations, such as shopping centers, factories, office buildings, etc.
The process for collecting blood is a relatively simple process with respect to the participation of a donor. However, the means for testing, typing, storing and preserving the collected blood requires relatively sophisticated techniques and equipment to minimize loss from contamination or spoilage.
Normally, blood is drawn from a donor through flexible tubing extending into a plastic blood collection bag. Once the bag has been filled to a pre-determined quantity/weight, the tubing must be sealed to easily separate and destroy the phlebotomy needle, to prevent leakage and, more importantly, to prevent contamination and deterioration of the collected blood. After collection, the blood must be typed and tested under various criteria. To provide a representative supply of blood for these typing and testing purposes, a plurality of blood filled segments of tubing are sealed from one another to provide a plurality of segregable sealed samples which are opened only for typing and testing purposes.
At many blood collection centers, such as those operated by the Red Cross, much of the manual labor is performed as charitable work by older persons. These persons are often physically handicapped by the natural processes of aging, by arthritis or by previous injuries. For these persons who perform the work of sealing segments of filled blood tubing, the operation of the equipment must require a minimum of effort, be easy to use after minimal instruction, and minimize operator fatigue.
To meet these needs, desk mounted sealers have been developed by the present assignee. U.S. Pat. Nos. (1) 4,186,292; (2) 4,390,832; (3) 4,529,859; and (4) 6,784,407 describe desk-mounted sealers usable by an operator who may be either seated or standing. The configuration of the desk sealers disclosed in these patents, which patents are incorporated herein by reference, provide a line of sight for the operator, whether seated or standing, thereby, operator fatigue is diminished and accurate positioning of the liquid filled tubing to be automatically sealed is promoted. Through actuation of a tubing position sensing switch or a foot operated switch, a seal will be effected in the tubing placed intermediate a fixed (positive) jaw and a moveable (ground) jaw thereby allowing the operator to use one or both hands to repetitively place and reposition the tubing intermediate the jaws. The housing of the desk sealer encloses the operative elements to protect them against seepage of fluid thereinto, whether from a burst liquid filled length of tubing or otherwise.
At mobile collection centers, hand held battery operated tubing sealers are generally used by phlebotomists due to the required mobility during the blood collection process at such locations. U.S. Pat. Nos. (5) 4,013,860; (6); 4,491,711; and (7) 5,349,166 assigned to the present assignee disclose various configurations of hand held tubing sealers, which disclosures are incorporated herein by reference. A hand held tubing sealer includes a body housing electronic circuitry for applying radio frequency (RF) energy to the tubing to be sealed and a power source. An electrical conductor extends from the body to a housing containing a circuit for generating the RF energy and the source of electrical power, such as a portable battery. The housing is usually supported on the person of the phlebotomist. The body of the hand sealer may also include further circuits for controlling the transmission of RF energy. A pivotable lever extends from the body and upon pivotal movement toward the body draws a moveable ground jaw toward a fixed jaw to compress the liquid filled tubing therebetween. Commensurate therewith, a switch is actuated to transmit RF energy from the fixed jaw to the moveable ground jaw as a function of the degree of compression of the liquid filled tubing placed therebetween. The RF energy transmitted heats the tubing to or close to the melting temperature to weld the side walls of the tubing with one another and form a seal therebetween. Transmission of RF energy is halted as a function of the relative position between the moveable ground jaw and the fixed jaw. Upon formation of the weld, the lever is released to permit the moveable ground jaw to be repositioned away from the fixed jaw and accommodate removal of the sealed liquid filled tubing.
As plastic is heated during transmission of the RF energy from the fixed jaw to the moveable ground jaw, dissipation of the heat must be accomplished quickly to prevent heat buildup both from an operator safety standpoint and to prevent premature melting of the tubing. The moveable ground jaw serves the function of a heat sink to accommodate conductive absorption and radiation of the heated plastic tubing. To enhance heat dissipation, the moveable ground jaw is formed as a relatively massive unit and it is configured to provide a relatively large surface area to encourage heat radiation and convective air cooling.
Numerous sealers for liquid filled plastic tubing have been developed, not only by the present assignee, but by numerous other entities. The major difficulty encountered during development of each of these sealers is that of controlling the melting of the tubing to form a strong seal between adjacent segments capable of withstanding centrifuging pressures imposed upon the liquid within the tubing segments without compromising the seal. Secondly, the serial sealed segments of liquid filled tubing must be easily separated from one another. That is, the seal between pairs of segments must be capable of being uniformly torn to separate the segments with low force and yet the seal for each segment must be maintained to contain the liquid in each segment.
It may be noted that pre-existing tubing sealers usually had a rib of rectangular cross-section formed on the ground jaw. This produced a channel across the tubing in the area of the seal. It defined the preferred location of tear between the adjacent segments.